Paramecuin

2000. The Journal of Arachnology 28:185–194

POPULATION STRUCTURE, SEASONALITY, AND HABITAT USE BY THE GREEN LYNX SPIDER PEUCETIA VIRIDANS (OXYOPIDAE) INHABITING CNIDOSCOLUS ACONITIFOLIUS (EUPHORBIACEAE)
Angelica M. Arango and Victor Rico-Gray: Departamento de Ecologıa Vegetal, ´ ´ Instituto de Ecologıa, A.C.; Apdo. 63; Xalapa, VER 91000 Mexico ´ ´ Victor Parra-Tabla: Departamento deEcologıa, F.M.V.Z. Universidad Autonoma de ´ ´ Yucatan; Apdo. 4-116; Merida (Itzimna) YUC 97000 Mexico ´ ´ ´ ´
ABSTRACT. For one year we studied the habitat use of Peucetia viridans living on Cnidoscolus aconitifolius, in a pasture land in Merida, Yucatan, Mexico. Highest spider density was recorded in August ´ ´ ´ (total 118, adults 77), and lowest in May (total 7, adults 2). Spider density wassignificantly higher in isolated plants and lower in plants in a patch. Sex ratio (&:() varied from 1:1.5 in April, to 1:1 in May, and to 1:0.1 in September. The dominant instar (both sexes) changed during the study. Throughout the study more spiders were recorded in ’repose’ than performing any other activity. Foraging and feeding were more intense between July and September, when their prey, flowervisitors, were more abundant. The number of spiders on plants varied spatially and temporally due to the combined effects of distance of the individual plant to the nearby forest, monthly precipitation, plant height, and number of panicles in anthesis. Forty-eight percent of the spiders were found living on plants with 20–30 panicles in anthesis (2% of the plant population). Most of the spiders (exceptfor adult females) were found either below or above leaves. There were no significant differences in the distribution of most stadia respective to plant height. Positive significant correlations were found between the number of spiders and the abundance of floral visitors when the data were compared shifted-back one month, and between the number of spiders and the number of panicles in bloom whenthe data were compared shifted-back two months. When the abundance of spiders, floral visitors and number of panicles in bloom were correlated to monthly precipitation, we found a positive significant correlation for spider abundance when the data were compared shifted-back three months, a significant negative correlation for floral visitors when the data were compared shifted-back two months, and anonsignificant correlation for the number of panicles in bloom, although both (panicles and floral visitors) peaked in May. Keywords: Peucetia viridans, Cnidoscolus aconitifolius, population structure, seasonality

Animals which are mobile during a period of their life actively select a site for nesting, feeding and reproduction. The latter may be influenced by parental habitat occupation, highdensity of competitors, or habitat availability at certain times of the year. The new site has to provide enough food, adequate nesting conditions, and protection against enemies and adverse weather conditions. Food resources are patchily distributed for most animals, regulating their feeding behavior, population dynamics, fitness and ultimately their evolution (Bronstein 1995). Thus, the fitness of ananimal should be directly influenced by its ability to find a suitable habitat, which is based on an innate preference for certain high-

quality environmental characteristics (e.g., absence of enemies and availability of food and shelter). Object organization in space is used to locate such habitats (McCoy & Bell 1991). Environmental characteristics exert a strong influence on habitat selectionin spiders (Uetz 1991). For example, spiders depend on the structure of the environment because: (1) they need attachment sites for their webs, and (2) their sensory organs are based on the recognition of tactile vibrations of the substrate (Rovner & Barth 1981; Uetz & Stratton 1982). Spider populations show certain associations between their structure and the heterogeneity and/or structural...